1. Field of the Invention
The present disclosure relates to methods for formulating electrolytes and electrolyte solutions useful in reduction-oxidation (redox) flow batteries.
2. Description of the Relevant Art
There is an increasing demand for novel and innovative electric power storage systems. Redox batteries have become an attractive means for such energy storage. In certain applications, a redox flow battery may include positive and negative electrodes disposed in separate half-cell compartments. The two half-cell compartments may be separated by a porous or ion-selective membrane, through which ions are transferred during a redox reaction. Electrolytes (anolyte and catholyte) are flowed through the half-cells as the redox reaction occurs, often with an external pumping system. In this manner, the membrane in a flow cell battery operates in an aqueous electrolyte environment.
In some applications, an iron-ion containing aqueous hydrochloric acid solution may be used as the catholyte, while a chromium-ion containing aqueous hydrochloric acid solution may be used as the anolyte. In some applications, a mixture of chromium and iron containing solutions may be used on both sides of the redox flow battery. The use of mixed reactants substantially eliminates the requirement for a highly selective membrane since the composition of both half cells is identical in the discharged state.
There is a need for electrolytic solutions that enhance the useful reactions occurring in a flow cell battery, while minimizing side reactions.